The National Geospatial-Intelligence Agency offers an impressive POI list called "Complete Files of Geographic Names for Geopolitical Areas", which seems to comprehensively cover every spot of the world.

Data.gov, the US government's open data warehouse, whose self-described purpose is to "increase public access to high value, machine readable datasets generated by the Executive Branch of the Federal Government" is celebrating its 3rd year of service.

The main area of the website contains some spatially-enabled data as well as links to external datasets, some of which are shapefiles or links to other websites.